Electrical heating element of large surface for low temperatures



Patented Nov. 19, 1935 sucrarcar. name or mass smacs roa LOW rim-- mucusIstvanl'ahalhfaludy Budap st. Hungary. sl-

Oathodique. seems I slsnorto laDlspes-slon Anonmmlelglnm No Drawlng.

Application November 6, 1933,

Serial No. 08,920. In the Netherlands Novem- 4 Claims.

The electrical heating elements in use up to now consist in most casesof resistance-bodies. such as wires wound helicaliy, gaunerwire cloth,bars of resistance material and the like, which in operation are broughtto incandescence or at least to high temperatures.

In heating a dwelling room, assembly hall or the like, such a hightemperature is undesirable, because the radiating heat is veryunpleasant, the dust particles present in the air are burnt on theheating elements, not to mention other disadvantages. A considerabledisadvantage consists in the fact that the radiating surface is smalland on account thereof a very unfavourable distribution of the heatresults.

For this reason, endeavours have already been made, particularly inconnection with the heating of rooms, but also for other purposes, tomanufacture electrical heating elements, which go distribute the heatover generated large surfaces and. by making use of a low temperature,avoid the drawbacks mentioned.

The best result is obtained in the following manner: a thin layer of thematerial, causing electric resistance, is deposited on a body which ismade of electrically non-conductive material. Such heating elements ofsmall size have already been manufactured, the metal to be applied beingprecipitated chemically and burnt in to firmly adhere.

Apart from the fact that it is not possible to obtain a heating bodywith a large surface by these means, because the layer of metal has notsufllciently uniform thickness, the following disadvantage stillremains. The metal becomes too coarse-grained and it is not possible tomake the layers as thin as desirable in order to avoid the necessity ofproviding on the heating element conductors of a greater length thanconvenient for practical use.

The invention relates to a heating element, on which the metal employedto set up resistance is applied in a very thin layer obtained however byother than chemical means. A metal covering of very great uniformity isobtained by applying the metal in vacuum by means of cathodic dispersionor by means of thermal evaporation of the metal. It is also possible toobtain thin precipitations of metal on non-conductive bodies, bygalvanic means, provided that these bodies are previously madeelectrically conductive by coating them with an extremely thin layer ofmetal by applying the latter in vacuum by means of cathodic dispersionor by means of the evaporation of the metal.

Such heating elements can be manufactured in any desired size, notablywith surfaces up to sev-j eral square meters and it is perfectlypossible to apply extremely thin layers of metal, which, thus produced,can be made of absolutely .uniform thickness. By these means it ispossible to bring the thicknes of the layer of metal to correspond tothe desired rate of load and particularly into accordance with the usualvoltage available, without having to make the conductor 10 of greaterlength than convenient for practical purposes, measured in the directionof the current.

It is therefore possible to employ heating sur faces on which a veryconsiderable amount of re- 15 sistance is provided, which accordinglyallow a relatively low amount of current to pass and which owing totheir large surfaces emit heat at low temperatures.

By way of example may be mentioned a glass 20 plate having a surface of1 x 1 m., being provided with a dull surface on one of its sides andcoated with platinum by means of cathodic dispersion or bythermal-evaporation of the metal, at a given voltage of 230 volts whichcarries a current of 2 26 amps. The energy absorption therefore amountsto 460 watts and 390 calories are emitted per hour at a temperature ofabout 40' C.

Another example is a slate plate of 1.3 sq. metre surface, which is madeelectrically conductive on one of its sides by means of a thin layer ofsilver applied by means of cathodic dispersion. On this layer, anotherlayer of nickel of such thickness as to make a current of 3.3 amps. passat a voltage of 230 volts, is applied by 35 precipitation. This plateemits about 630 calories per hour at a temperature of about The layer ofnickel applied in the manner described at the same time also protectsthe layer of silver against oxidation. 40

In the described manner it is possible to manufacture heating elementsfor all temperatures from the lowest up to a temperature ofincandescence. In the heating of rooms, these heating elements thespecial advantage of provid- 5 ing the low temperature which hereby isdairable in this connection as well as the uniform distribution of theheat over a large surface.

In view of the fact that the layers of metal are so extremely thin (apractical figure is about 6 millimicron) the required quantity of metalis so small as to enable precious metals such as platinum and gold, tobe employed without dimculty, thus enabling these heating elements tobsusedalsoincaseawherealayerofordinary metal would be exposed to thechemical action of gases, acid fumes, etc.

It has, moreover, been found that it is quite possible to make the layerso thin that it rea mains transparent and on account thereof may beemployed for very special purposes. By way of example may be mentionedthe heating of a portion oi the front window panes of motorcars andother vehicles in order to prevent the 10 panes becoming dimmed by snow,rain, haze, etc. A very thin plate of mirror glass covered with goldused as heating element generates about 100 calories per hour with acurrent of 10 amps. passing through it at a voltage of 12 volts. In

15 the case of heating elements of this kind it will generally bedesirable to arrange the layer of metal between two glass plates.

At certain places as for instance where the current enters and leavesthe heating element,

90 it is possible to make the layer of greater thickness either byapplying a greater quantity 01' metal, possibly also a diflerent kind ofmetal at thue places, or by applying the metal by galvanic means. V

I l'brspecialpurposesitisalsopossihletoapplyontheheatingsurtacecoatsotothermaterialsaswelhproducingacatalyticoranemitting action.

Having thus described my invention, what Iclaimasnewanddesiretosecurebyletterslat g eat is:

1. An electrical heating element, comprising a cathode sputteredconducting layer of uniiorm thickness of not over one micron on aninsulating M99 1.

2. An electrical heating element, comprising a cathode sputteredconducting layer of uniform thieknesoinotoveronemicrononaninsulatingsupport, said layer being produced in vacuo.

3. An electrical heating element, comprising a u cathode sputteredconducting layer 0! uniform thicknessotnotoveronemicrononaninsulatingsupport, said support being transparent.

4. an electrical heating element, comprising a cathode sputteredconducting layer 0! uniionn l0 thickness of not over one micron on aninsulatipzgiemsupport, said layer and support being trans- IBTVAN PUHAKIBFALUDY.

